A supersonic bullet generates a conically shaped expanding shock wave called a Mach-cone where the local and temporal air turbulence effects can be characterized by a steep change in ambient air pressure (shock front) which expands radially outward from the bullet path. The acoustic energy of the shock front can be detected by acoustic sensors.
There are several techniques to measure the velocity of bullets. Prior art chronograph solutions known to be used at shooting ranges are based on optical sensor technology. However use of acoustic sensors for measuring the velocity of bullets is also mentioned in the state of the art.
U.S. Pat. No. 5,349,853 discloses bullet sensors that measure the time when a bullet passes the monitored plane of the sensors cooperating with a device for calculating a velocity based on these measurements.
WO9805971 discloses a targeting apparatus comprising a plug-together sensor array and a base station for display and analysis. A projectile target is surrounded with a sensor array. The base station receives projectile impact data and displays information corresponding to the data.
A problem with known solutions is that they require set-up of plug in sensors along the shooting range, thus requiring substantial preparation prior to shooting. The present invention seeks to provide an improved device for measuring the velocity of a bullet.